What is the theme in The Killing Game by Iris Johansen?

Knowing where children are is a theme of the book. A common commercial on television reminds parents that it is late and asks them if they know where their children are. However, it takes on a new meaning when this becomes the theme of The Killing Game. These children may have been kidnapped and killed. They may have run away and gotten caught in a sex-slave ring. These missing children of the Duncan series of books are not just out cruising the mall and getting into mischief around the neighborhood. These children don't come home. They may be missing for years. Some are never found. Eve hunts them and brings them back to parents for burial. These children and MIA military have much in common. Their parents don't know what happened to them. Eve tries to get closure for such parents, one family at a time.